Manufacturers use sell-by or best-by dates on their products so grocers will know how long to display the product for sale. This protects the manufacturer's reputation as a creator of delicious, tasty foods.
Sell-by and best-by dates are not ‘safety dates.' As long as you've stored the unopened product properly, you can probably eat it well beyond the printed date. For example, according to the U.S. Department of Agriculture, eggs are "perfectly safe to eat… three to five weeks of the date you purchase them," regardless of the carton's sell-by date.